The present invention relates to a technique of rewriting a program and, in particular, relates to a technique of rewriting data of programs of control apparatuses efficiently and safely in a system in which the plurality of control apparatuses are coupled via a network within a vehicle.
In a system having a plurality of control apparatuses, there is a case where the program data of a particular one of the plurality of control apparatuses is required to be rewritten. For example, in most cases, a plurality of control apparatuses are provided within the vehicle body of an automobile. The program of such the control apparatus is generally stored in a ROM. Conventionally, in the case of rewriting the program within a ROM, the program data of each of the control apparatuses is rewritten. Such a conventional technique is disclosed in JP-A-6-272611, for example.